Halogen containing derivatives of dicarboxylic acids



Patented Oct. 18 1949 UNITED STATES PATENT OFFICE.

HALOGENCONTAINING DERIVATIVES OF DICARBOXYLIC ACIDS No. Drawing.Application October-25, 1947, Serial No. 782,220

6 Claims.

This invention relates, to the synthesis of a new class of chemicalswhich are dialkyl esters of alpha-bromo-beta-trichlromethyl succinicacid by the free radical initiated addition of trichlorobromomethane todialkyl esters of one of the alpha, beta-ethylene dicarboxylic acidsmaleic and fumaric.

Organic compounds containing olefinic unsaturation can be caused toreact with trichlorobromomethane so as to form simple one to one adductswhich contain in each molecule the constituent atoms from one and onlyone molecule of the olefinic compound and the constituent atoms from oneand only one molecule of trichlorobromomethane. The methods of carryingout this reaction and the products obtained thereby are described morefull in my copending application Serial No. 696,941, filed September 13,1946, now Patent No. 2,468,208, dated April 26, 1949. I have now foundthat trichlorobromomethane can be caused "toreact *with dialkyl estersof either fumaric or :maleic acid to form useful halogen containingcompounds which are one to one adducts of trichlorobromomethane and theethylene dicarboxylic acid and have the in which R is a saturatedaliphatic hydrocarbon radical. This product may be easilydehydrobrominated to give a mixture of isomers having 7 I the typeformula RO-FCH This dehydrobrominated product, when hydrolyzedcompletely, loses CO2 and is converted into fumaric acid.

In the course of the reaction producing the 5 dialkyl succinate and onemolecule of the dialkyl 50 alpha, beta-ethylenedicarboxylic acid havingthe type formula This compound can be dehydrobrominated to yield a 1,1,1trichloro-2,3,4,5-'tetracarboalkoxy pentene-4 which can be hydrogenated,hydrolyzed and decarboxylated to yield tetracarboxylic acid.

In the process of producing the dialkyl esters of alpha bromo-betatrichloromethyl succinic acid and the tetra alkyl esters of1,1,1-trichloro- 5-bromo-2,3,4,5-tetracarboxylic acid, a mixturecontaining trichlorobromomethane and a dialkyl ester of either fumaricor maleic acid is subjected to the. action of a free radical reactioninitiator such as either actinic light or a peroxide polymerizationcatalyst until the adducts are formed which may then be isolated as byfractional distillation.

Actinic light either visible or ultraviolet, i. 8., in frequency rangingfrom about 2500 A. to

about 5000 A. is preferred as the free radical reaction initiatoralthough peroxidic polymerization catalysts such as the diacyl peroxidesmay be employed equally well. Suitable peroxidic polymerizationcatalysts are, for example, the diacyl peroxides such as dibenzoyl anddiacetyl peroxide, tertiary butyl hydroperoxide, hydrogen peroxide,alkali peroxysulfates and the like.

Suitable dialkyl esters of ethylene alpha, betadicarboxylic acids arethe dialkyl iumarates and dialkyl maleates.

Suitable dialkyl fumarates are those of the lower aliphatic alcoholscontaining from 1 to 6 carbon atoms although, esters of higher alcoholsmay be used. Exemplary of such dialkyl fumarates :are diisopropylfumarate, di-n-butyl fumarate, diisobutyl fumarate, ditert-butyl fu-Equation 1 represents the addition of a free trichloromethyl radical toa dialkyl ester of an alpha,-beta-ethylenedicarboxylic acid 1 to form adialkoxy trichloromethylsuccinyl free radical which as in Equation 2 canremove a bromine atom from bromotrichloromethane to form an alpha bromobeta trichloromethyl succinate ester (III) and generate afreetrichloromethyl radical which can participate in the reaction ofEquation 1 and so give rise to a chain reaction. One of thetrichloromethyl dialkoxysuccinyl free radicals (II) 'formed according toEquation 1 can add to a molecule of dialkyl ethylenedicarboxylic acid toform the radical (IV) as shown by Equation 3. This free radical (IV) canthen remove a .bromine atom from bromotrichloromethane to form amolecule of a tetraalkyl ester of1,1,1-trichloro-5-bromo-2,3,4,5-pentane tetracarboxylic acid (V) andgenerate a free trichloromethyl radical as shown by Equation 4. The freetrichloromethyl radical formed by Reaction'3 can by participating ineither Reaction 1 or 3 serve to initiatea chain reaction. Equation 5illustrates the dehydrobromination of thealphabromo-beta-trichloromethylsuccinate ester III to form the dialkylester of beta-trichloromethylalpha, beta-ethylene-dicarboxylic acid(VI). Equation 6 illustrates the hydrolysis and decarboxylation ofproduct (VI) to give fumaric acid. Equation 7 illustrates thedehydrobromination of the tetralkyl ester of 1,1,1,-trichloro-5-bromo-2,3,4,5-pentane tetracarboxylic acid (V) to give 1,1,1trichlorol-pentene-2,3,4,5-tetracarboxylic acid (VII). Equation 8illustrates the conversion of VII to the orthoester VIII by reactionwith sodium alcoholate. Equation 9 illustrates the conversion of theorthoester VIII to the penta-ester IX by partial hydrolysis. Equation 10illustrates the hydrogenation of the pentaester to give the alkyl esterof '2,2,3,4,5-pentanepentacarboxylic acid X. Equation 11 illustrates thehydrolysis and decarboxylation of X to give 1,'2,3,4-butanetetracarboxylicacid XI.

The initial formation of the free trichloromethyl radicals necessary forstep 1 may take place according to either of the following two sets ofequations:

Equation 12a represents the thermal decom- EXAMPLE. 1

Photochemical induced addition of bromotrichloromethane to dimethylfumarate A mixture of bromotrichloromethane (198 g., 1.0 mole) anddimethyl fumarate (36 g., 0.25 mole) is internally irradiated by amercury vapor neon, fluorescent tube for twenty-four hours. Thetemperature of the reactants is maintained at 50-60 C. by theilluminating coil. The undissolved, crystalline fumarate estercompletely disappears in fifteen hours. Unreacted bromotrichloromethane(155 g.) isrecovered bydistillation at 101-104 C. at atmosphericpressure. Further distillation of the Viscous residue (75.5 g.) at 50.1'mm. yields 2 g. of unchanged dimethyl fumarateat "75-90 0. acolorless oil (fraction I) (5 7 g.) at '95-108 C.-which partlysolidifies and a viscous, light yellow oil (fraction II) (11.9 g.) at180-185" C. A black, viscous residue (4.1g) .remains. Hydrogen bromideis evolvedduringthe latterpart of the distillation.

The solid from fraction I is separated fromthe oil and after twicerecrystallizing from. methanol gives a white crystalline solid (M. P.5455 C'.) with a halogen analysis consistent with 1,1,1,-trichloro-3-bromo-2,3-di-carbomethoxypropane.

Anal. Calcd. for C1H8O4BrCl3: Ag equiv.,.85.6. Found: Ag equiv., 64.8.

EXAlVIPLE? 2 Photochemical-induced addition of bromotrichloromethane todimethyl maleate A mixture of bromotrichlorom'ethane'(132 'g., 0.66'mole) and dimethyl maleate (48 -g., 0.33 mole) is internallyirradiated'by a mercury vapor neon, fluorescent tube for twenty-fourhours. The temperature'of the reactants ismaintained at 50-60 C. by theilluminating coil. A crystalline deposit begins forming on the Wallsof'the "outside tube after one hour, reaching a maximum quantity in fourhours,-and nearly completely disappearing after twenty-four hours.The-reaction mixture is cooled andfiltered from 13 g. of crystallizeddimethyl fumarate. 'Unreacted bromotrichloromethane (84 g.) is recoveredby'd-istillation at101-103 C. at atmospheric pressure. Furtherdistillation of the higher boiling residue-at .2'mm. yields 115g. ofdimethyl fumarate'butrno dimethyl 'maleate. A colorless liquid (34.7 g.)which later solidifies (M. P. 53-55 C.) 'distillsat '110-120-C. andgives no lowering of the melting point on mixture with the white solidfrom 'fraction I of Example 1. Alight yellow-viscous oil (8.5g) distillsat ISO-190 C.with evolution-0f hydrogen bromide.

methyl fumarate addition product. (.1;1,1-trichloro-3-'bromo-2.3-dicarbomethoxypropane) "The crystalline additionproduct from fraction 1, Example 1, has a molecular weight of 341.0 asindicated by the benzene freezing-point lowering method. The calculatedmolecular weight of C'IH804BIC13 is 342.5. On treatment ofthe additionproduct (10 g.) with an equimolar amount of sodium methylate in methanolunder nitrogen, the temperature rises to C. and solid sodium bromideseparates. After three hours of intermittent refluxing water is added tothe mixture followed by ether extraction. On distillation of the etherextract, a water-white, slightly viscous oil (6.3 g.) (nn 1.4845)distills at '75-80 C. at 5 .1 mm.

Anal. calcd. for C7H'zO4Cls: CI, 40.8; found:

Cl, 41.2. Molecular Wgt. calcd. for C7H1O4Cla: 261.5; found: 262.9.

Hydrolysis of the white solid (4 g.) using 70 sulfuric acid gives ayellow, turbid solution which is diluted with water and extracted withether using a continuous extractor. The crystalline extract (0.11 g.)remaining after evaporation of the ether is decolorized over charcoaland recrystal- 7 lized from methanol. These crystals melt at 284-287 C.and do not depress the melting point of an authentic sample of fumaricacid.

EXAMPLE 4 Molecular weight determination on the 2:1 addition product(fraction II) of Example 1 indicates that some hydrogen bromide may havesplit out at the high temperature of the distillation. Treatment of 10.5g. of the addition product in the cold with one-third mole ratio ofsodium methylate in methanol for one hour yields a precipitate of sodiumbromide. Extraction of the water-diluted solution with ether gives atar, 5.5 g. of which distills at 1'75-180 C. at .1 mm. and has a halogenanalysis consistent with 1,2,3,4-tetracarbomethoxy-5,5,5-trichloropentene-1.

Anal. calcd. for C13H15O8C132 Cl, 26.3; found: Cl, 26.6. Molecular wgt.calcd. for CiaHisOaclsz 4055; found: 404.0.

4.0 g. of the unsaturated 2:1 addition product VII is refluxed with a4.5 mole ratio of sodium methylate in methanol under nitrogen for sixhours. The crystalline sodium chloride is separated and the orthoesterdecomposed by acidification'with acetic acid. The reaction mixturediluted with water is extracted with ether and the oily extractdistilled at 145-155 C. at .2 mm. The penta-ester distillate (.3259 g.)is quantitatively hydrogenated using Adams catalyst.

Quant. hydrog. calcd. for Ciel-119010: 21.0 ml., std. condits. Absorbed:19.2 ml., std. condits.

The hydrogenated penta-ester is hydrolyzed and decarboxylated byrefluxing in dilute hydrochloric acid. After extracting with ether andevaporation of the ether, a white solid (.11 g.) melting at 185-186" C.remains. Auwers (Ber., 26, 364 (1893)) lists the melting point of1,2,3,4- butane tetracarboxylic acid at 189. The acid (.0986 g.) gives aneutral equivalent of 63.4 usin phenolphthalein indicator and 15.49 ml.of .1012 N sodium hydroxide.

EXAMPLE 5 A mixture containing 198 grams of bromotrichloromethane, 36grams of dimethyl maleate, and 0.65 gram of benzoyl peroxide is heatedto between 80 and 90 C. for three hours. At the end of that time 25.0grams of dimethyl fumarate, 2.5 grams of dimethyl maleate, 11.3 grams ofa product identical with fraction I of Example 1 and 3.6 grams of aproduct identical with fraction II of Example 1 are isolated.

EXAMPLE 6 A mixture containing 198 grams of bromotrichloromethane, 36grams of dimethyl fumarate, and 0.65 grams of benzoyl peroxide is heatedto -90 C. for three hours. At the end of that time 10.5 grams ofunreacted dimethyl fumarate, 39.8 grams of a product identical withfraction I of Example 1, and 9.2 grams of a product identical withfraction II of Example 1 are isolated.

I claim:

1. The process of producing 1,1,1-trichloro-3- bromo-2,3-dicarbalkoxypropanes and 1,1,1-trichloro-5-bromo-2,3,4,5-tetracarbalkoxy pentaneswhich comprises maintaining trichlorobromomethane and a dialkyl ester ofone of the ethylene alpha, beta-dicarboxylic acids maleic and fum'aricin contact with a peroxidic polymerization catalyst until1,1,1-trichloro-3-bromo-2,3-dicarbalkoxy propane and1,1,1-triohloro-5-bromo-2,3,4,5- tetracarbalkoxy pentane are formed.

2. A chemical chosen from the class consisting of1,1,1-trichloro-3-bromo-2,3-dicarbalkoxy propane;1,1,1-trichloro-5-bromo-2,3,4,5-tetracarbalkoxy pentane and theirdehydrobrominated derivatives.

3. A chemical which is a 1,1,1-trichloro-3- bromo-2,3-dicarbalkoxypropane having the type formula MORRIS S. KHARASCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,199,799 Jacobson May '7, 19402,297,351 Gerhart Sept. 29, 1942 2,313,501 Bachman Mar. 9, 19432,394,512 Coleman Feb. 5, 1946

